IQ not fixed in the teen brain, study shows

by Gisela Telis - Oct. 21, 2011 12:00 AMScienceNOW

A new study confirms what parents have long suspected: Adolescence can do a number on kids' brains.

Researchers have found that IQ can rise or fall during the teen years and that the brain's structure reflects this uptick or decline. The result offers the first direct evidence that intelligence can change after early childhood.

Although researchers debate what IQ tests actually measure, they agree scores can predict ability to learn and perform certain tasks, and to some degree forecast our later academic achievement and job performance. Scores have long been thought to stay relatively stable throughout our lives; the few studies that have shown some variation could not rule out measurement errors or differences in testing environment as the cause.

So neuroscientist Cathy Price of University College London and colleagues looked beyond the scores. They tested 33 teenagers - 19 boys and 14 girls - in 2004, when they were 12 to 16 years old, and again in 2008, when they were 15 to 20 years old. Each time, the teens took IQ tests that measured their verbal and non-verbal abilities. Then, using magnetic resonance imaging, the researchers scanned the teens' brains while they performed verbal tasks, such as reading or naming objects, and non-verbal tasks, such as solving visual puzzles with their hands. The idea was to match their test scores with a picture of their brain's structure and activity.

The test results revealed dramatic changes: between testings, the teens' verbal and non-verbal IQ scores rose or fell by as many as 20 points (on a scale for which the average is 100). Some teens improved or declined in just verbal or non-verbal skills or improved in one area and declined in the other.

The brain scans mirrored the differences. In teens whose verbal scores had increased, for example, the scans showed increased gray-matter density in a region of the brain activated by speech. Teens whose non-verbal skills improved showed changes in a brain region associated with motor movements of the hand.

"These changes are real, and they are reflected in the brain," says Price, whose team reports the finding in Nature online. "People's attitude is to decide early on that this is a clever kid, and this is not a clever kid - but this suggests you can't make that assessment in the teenage years."